Absorbent product



United States Patent Gfifice 3,067,745 Patented Dec. 11, 1962 a corporation of New Jersey No Drawing. Filed Aug. 12, 1959, Ser. No. 833,151 1 13 Claims. (Cl. 128285) This invention relates to absorbent products and more particularly to absorbent products, such as tampons, which function as media for absorbing body fluids and also function'as acidifying and buffering media.

The normal, healthy vagina is weakly acidic and has a pH of approximately 4.5. This acid condition of the vagina provides an effective barrier against the growth of pathogenic microorganisms normally associated with nonspecific vaginal infections because such microorganisms do not grow below a pH of about 5. If, however, the pH of the vagina becomes less acidic, i.e., more than about 5, the pathogenic microorganisms tend to grow. A change in pH of the vagina from the normal of about 4.5 to 5 to a more alkaline pH may be brought about by various vaginal conditions and may occur at any time during the menstrual cycle. During menstruation, particularly, the vagina becomes less acid due to the presence of menstrual fluid which has a pH of from about 7 to 8. As a result, the protective barrier provided by the normal acidic condition of the vagina becomes less effective, thereby providing an environment favorable to the growth of the pathogenic microorganisms.

To overcome the reduction in acidity of the vagina which is favorable to the growth of the pathogenic microorganisms, and to re-establish the desired normal acid condition, different formulations and techniques have been developed. Such efforts have included th development of formulations, such as jellies, powders, suppositories, and the like containing acidifying materials which are introduced into the vagina in their prepared form. Other attempts have included physically incorporating acidifying materials into the absorbent products by coating, spraying, impregnating and the like, to impart to such products acidifying properties.

- While the above-mentioned types of products have met with acceptance, they are subject to numerous disadvantages. The jellies, powders, and suppositories containing acidifying materials may be inconvenient to handle and apply and are not fully retained in the vagina and tend to escape. In addition, they do not have capacity for absorbing vaginal fluid which may be present in the vagina, particularly during menstruation. Therefore, to use such products during menstruation, it is also necessary to use a catamenial tampon or similar article at the same time. The absorbent products having acidifying material physically associated with them have reduced absorbing abilities and absorbing capacities as well as a decrease in softness, resiliency and flexibility. In addition, the acidifying material is not always retained in the absorbent products and tends to separate from the absorbent products because of the manner in which it is physically associated with them. Further, a number of such products do not exercise their acidifying properties directly upon insertion into the vagina.

I have found that an absorbent product, such as a catamenial tampon, having acidifying properties to counteract a reduction in acidity of the vagina, especially during menstruation, may be provided by making the product from fibrous material which absorbs body fluids and which also has acidifying properties which are an integral part of the fibers. Suitable fibers for making the tampon of the invention include fibers having cation exchange properties obtained by chemically modifying I the fibers in such a manner that the fibers have chemically associated with them exchange groups in the hydrogen form. In addition, such fibers sequester nutrients essential to the growth of the microorganisms. The fibers are so modified that their physical characteristics, such as their stiffness, resiliency, flexibility, coherence and absorbency, are substantially the same as those in the unmodified fibers with the result that a product made from such modified fibers has the desirable attributes of comfort and absorbency present in a product made from unmodified fibers. In addition, due to their fibrous form, the fibers can be processed on conventional tamponmaking machinery and lend themselves readily to tampon manufacture.

The fibrous materials ordinarily used to make absorbent products, such as catamenial tampons, are usually cellulosic. Cotton and rayon, because of their highly absor-bent properties, have been found particularly suitable. These cellulosic materials may be chemically modified to form cellulosic derivatives which have acidifying properties and at the same time retain essentially their original fibrous characteristics, thus permitting their use in absorbent products requiring a fibrous form and requiring the absorbent capacities obtainable with such fibers. For use in tampons, the fibers are so modified that they are essentially water insoluble so that they retain their fibrous form in order that they may be Withdrawn from the vagina after use. Examples of such modified cellulosic materials include cellulose acid succinate, cellulose acid maleate and cellulose acid malonate; tricarboxylic acid esters, such as cellulose acid citrate; mineral acid esters, such as cellulose acid sulphate, phosphorylated cellulose and sulfonated cellulose; cellulose ac1d others, such as carboxymethyl cellulose, carboxyethyl cellulose; cellulose anhydrides, such as cellulose carboxymethyl anhydride; alkyl sulfonic acid ethe-rs, such as sulfoethyl cellulose; phosphono alkylated celluloses; and mixtures thereof.

The acidifying materials contemplated and which fulfill the above requirements are fibrous celluloses wherein the cellulose molecules have one or more hydroxyl groups removed and an ester or ether residue containing at least one free organic or inorganic acid radical substituted therefor. Such materials may be represented generally by the formula Cell.(O-X) wherein Cell. represents the residue of a cellulose molecule, n the number of hydroxyl groups which have been removed from the cellulose molecule, and X an acidic ester or ether group in hydrogen form.

The acidifying capacities of the modified cellulosic fibers are related to the extent to which and the manner in which the fibers have been chemically modified and more specifically are related to the degree to which the hydroxyl groups in the cellulose molecules have been substituted for by the acid radicals and to the type of the substituent acid radical. The degree of substitution of the fibers and consequently the acidifying capacity of the product made from the fibers, can thus be regulated to provide the results desired under conditions of use.

The methods of preparing the cellulose derivatives useful in practicing the present invention are known in the art. The derivatives are so prepared that the cellulosic materials are essentially water insoluble, retain their general fibrous structure and form and preferably are of cardable length. The following are given by way of example for making some of the derivatives:

Example I of 25% aqueous sodium hydroxide. The temperature is raised to between 61 C. and 78 C. and the reaction started. Ten minutes after the start of the reaction, the pH is adjusted to 12 by the addition of approximately 200 ml. of 50% sodium hydroxide solution and the reaction continued for 65 minutes thereafter.

The fibers are centrifuged and then saturated with a solution of 125 grams chloracetic acid in 325 ml. of isopropyl alcohol. The temperature is maintained between 50-64" C. and the reaction carried out for one hour. The carboxymethylated fibers are next washed to neutrality, using first 80 vol. percent aqueous isopropyl alcohol, then 20 vol. percent acetic acid in isopropyl alcohol, and finally again with 80 vol. percent aqueous isopropyl alcohol. Conversion of the modified fibers into the hydrogen form is carried out by steeping them for 30 minutes in a solution containing 20 vol. percent concentrated hydrochloric acid and 80 vol. percent isopropyl alcohol and then repeating. The fibers are centrifuged after each treatment and after the final steeping are washed to a pH of 3.7 in 80 vol. percent aqueous isopropyl alcohol. The acid exchange capacity of the converted carboxymethyl cellulose fibers formed is about 0.17 meq./ g. The degree of substitution is about 0.28.

Catamenial tampons made from the carboxymethylated cotton fibers closely resemble tampons made from untreated cotton in appearance and wearing comfort. The absorbing capacities of the tampons are approximately the same as tampons made from untreated cotton.

Example 11 100 grams of bleached cotton are impregnated with a solution consisting of 200 grams phosphoric acid, 325 grams urea and 345 grams distilled water. The fibers are then centrifuged and cured for 40 minutes at 140-15 8 C., washed with distilled water, then with 1% hydrochloric acid and finally again with distilled water until the chloride reaction becomes negative in the filtrate. The phosphorylated fibers are then centrifuged and dried at 45 C. The acid exchange capacity of the fibers is about 3.2 meq./ g. The degree of substitution is about 0.52.

Catamenial tampons made from the phosphorylated fibers have an absorbing capacity of 2.7 ml./ g. and closely resembled ordinary cotton tampons in appearance and wearing comfort.

Example III The phosphorylated cotton of Example II is blended with an equal weight of bleached absorbent cotton and made into catamenial tampons. The tampons have physical and absorbency characteristics similar to those prepared from phosphorylated cotton.

The acidifying capacities of the above modified cellulosic fibers with respect to menstrual fluid were determined by electrometric titration methods. 0.25 gram of the fibers were dispersed in 10 m1. of distilled water. After determining the pH of the fiber slurry, menstrual fluid was introduced in small increments from a burette in such amounts as to provide a fluid to fiber ratio ranging from 0.8 to 12.0 ml./g.

After each addition of each increment of menstrual fluid the mixture was thoroughly stirred and the pH values recorded when the readings became constant. The tests were extended to include a fluid to fiber ratio of 12.0 ml. of fluid per gram of fiber to illustrate the acid reserve capacity of the fibers. In each case, six tests were conducted using six different menstrual fluids collected with intravaginal cups and the average obtained. As a control, tests were conducted on unmodified absorbent cotton.

The pH of the menstrual fluids used in determining the acidity of the unmodified cotton fibers and the carboxymethylated cotton fibers ranged from 7.13 to 7.92 and averaged 7.47. In the vase of the phosphorylated cotton fibers and the blend of phosphorylated cotton and unmodified cotton fibers, the fluid ranged in pH from 7.29 to 8.52 and averaged 7.88.

Blend of Unmodified Carboxy- Phosphorylbleached Ml. of fluid cotton methylated ated cotton and per gram (initial pH cotton cotton phosphory lof fiber 5.46) average (initial pH (initial pH ated cotton of 6 tests 3.20) average 2.77) average (initial pH of 6 tests tests 3.04) average of 6 tests 0. I 27. 9 3.31 1: 3. 92 1. 4.13 3. 01 3 58 2. 4 32 3.13 3 3. 4 43 3. 26 3 94 4. 4 59 3.39 4 10 4. 4. 66 5. 4. 74 6. 3. 65 4. 38 8. 4 99 3.89 4.65 10. 4. l0 l2. 4. 26

The tests demonstrate that the initial pH of unmodified absorbent cotton is slightly acid. Its acidifying capacity is, however, exceedingly low and is neutralized rapidly with menstrual fluid, thus indicating that such fibers do not provide any significant buffering in the regions of a relatively low pH. The modified cellulosic fibers maintain a fairly even acid pH from the start of the application of menstrual fluid until the fibers are saturated. Further, at the point at which a conventional tampon would be saturated, e.g. from about 2.5 to 3 ml. of fluid per gram of fibers, the fibers still have an appreciable amount of reserve acidity and are thus capable of neutralizing more than those amounts of menstrual fluid ordinarily absorbed by a conventional tampon before it is discarded and replaced, and still maintain the desired acid pH. As illustrated in the table, tampons made from phosphorylated cotton would have a relatively high reserve acidifying capacity; even at a ratio as high as 12 ml. of menstrual fluid per gram of phosphorylated fibers, the pH was still appreciably below 5.0. Fibers of the phosphorylated type may, therefore, be readily mixed with other fibers. The fibers, due to their high reserve acidity, may be blended with other fibers in varying percentages and still contain suflicient reserve acidity to neutralize the quantities of menstrual fluid normally encountered in the use of tampons and still provide the acid pH desired in the vagina.

The above examples further illustrate that the reserve acidity of tampons made from the modified fibers may be suitably varied over wide ranges. In the above example, the carboxymethylated cellulose had a comparatively low degree of substitution and a relatively low acidity. In comparison, the phosphorylated cellulose was more highly substituted and had a relatively higher resevere acidity. In addition, the nature of the substituent group may be varied to provide more or less reserve acidity, as desired, or to provide a buffering at a higher or lower pH. If the substituent group is a weak acid, it will be buffered at a relatively high pH; if it is a strong acid, it will be buffered at a low pH. In each instance, therefore, the amount of modified cellulosic fibers desired for a particular application can be suitably varied by using fibers having a higher degree of substitution; e.g. increasing the number of acid groups on the residue of the cellulose molecule, or by using different substituent acid groups.

The menstrual fluids collected for the tests were found to vary in pH and also in bufiering capacity. The pHs ranged from 7.29 to 8.52 and averaged about 7.6. The variance in the buffering capacities is believed to be due to the nature of the constituents of the fluid, such as the amino acids, and to the amounts in which they are present. Therefore, in preparing the tampon of the invention, the acidifying capacity of the tampon may be varied, e.g., it may be made sufficient to maintain a pH in the vagina about 5 or below; or to neutralize menstrual fluid having an average pH and buffering capacity, but preferably to neutralize a menstrual fluid having a pH at the high end of the range, e.g., about 8, and having the greatest bufiering capacity, and also to establish a pH in the vagina of below 5. The tampons are desirably so made as to maintain a pH in the vagina ranging from about 1.5 to about 5, and preferably from about 3.5 to 4.5. If designed for use during menstruation, they are preferably made to absorb from about to about cc.s of menstrual fluid and to neutralize such amounts of fluid having a pH from above 7 to about 8 and also to provide a pH in the vagina within the ranges of from about 1.5 to about 5.

The acid exchange group may be introduced into the cellulosic material at any suitable stage in the manufacture of the absorbent product. The raw materials, e.g. cotton fibers, may be chemically modified before processing to form the tampon, or the fibers may be modified after the tampon is made from such fibers. As a practical matter it has been found preferable to modify the fibers before the tampon is made.

The tampon may contain natural cellulosic fibers, such as cotton, or synthetic fibers, such as rayon, which may be completely substituted, partially substituted, or

blended in various ways with chemically unmodified fibers. If desired, the fibers employed in the tampon may be in the form of yarns, woven or non-Woven fabrics, card webs, isotropic webs, and paper-like webs, although fibers of cardable lengths are preferred. The tampon of the present invention may have the usual elongated cylindrical form made'by highly compressing the fibrous material in a die tothe shape desired. By way of example, suitable tampons incorporating the invention and weighing 2.5 grams may bemade from the above carboxymethylated fibers by taking that weight of fibers and forming them into a tampon. A tampon of like weight may be made from the above phosphorylated cotton fibers by blending 1.25 grams of the fibers with 1.25 grams of unmodified absorbent cotton and forming into a tampon.

Conventional commercial tampons range in weight from about 1.8 to about 3 grams. Although they are capable of absorbing from about 5 ml. of menstrual fluid in the lower part of the range to about 10 m1. of fluid in the upper part of the range, they are ordinarily discarded before they become saturated and usually when they have absorbed about one-half of the amounts of menstrual fluid they are capable of absorbing, e.g. from about 2.5 to about 5 ml. Therefore, in preparing tampons within the commercial sizes incorporating the invention, it may be desired to provide them with suflicient acidifying capacity to neutralize from about 2 /2 to about 10 cc.s of menstrual fluid, and also provide the desired pH.

The buffering capacity and the alkaline characteristics of menstrual fluid are not fully understood. It has been determined, however, that in the region of pH 5 and above menstrual fluid has an alkalizing capacity approximating that of N/ 10 sodium hydroxide. Below this pH menstrual fluid exhibits a buflering capacity for which additional acidifying material should be provided. In view thereof, a suitable way of determining the amount of acidifying capacity to be impartedinto the tampon is to measure the acidifying capacity of the material to be used therein in accordance with the method disclosed by Guthrie in Industrial Engineering Chemistry, volume 44, No. 9, pages 2187-88, wherein the acidifying capacity of the material is measured by titrating with N/ 10 sodium hydroxide.

A tampon of general application can be prepared by providing therein fibers having sufficient acidifying capacity to neutralize about 4 ml. of N/ 10 sodium hydroxide per gram of fibers, and suflicient reserve acidity to provide a pH not exceeding about 5. If it is desired to bring the pH of the vagina to about 1.5, a fibrous material such as sulfoethyl cellulose in the hydrogen form at pH 0.2 with cation'exchange capacity of 0.34 milliequivalents per gram may be used. This amount of this material will neutralize 25 ml. 10/N sodium hydroxide and bring it to a pH of about 1.5.

By way of further example, in view of the fact that conventional tampons are usually, but not always, dis cardedbefore they are fully saturated, it may be desired to provide a commercial tampon in the lower part of the range of conventional sizes, e.g., weighing 1.8 grams with sufiicient acidifying capacity to neutralize 2.5 cc.s of menstrual fluid and a tampon in the upper part of the range, e.g., weighing 3 grams, with suflicient acidifying capacity to neutralize 12 ml. of N/ 10 sodium hydroxide. The smaller tampon may be prepared by providing it with sufiicient acidifying capacity to neutralize about 3.5 ml. of N/ 10 sodium hydroxide and to provide a pH not exceeding 5 and the larger tampon prepared by providing it with suflicient acidifying capacity to neutralize 12 ml. of N/ 10 sodium hydroxide, and to provide a pH not exceeding 5.

In use, the tampon may be inserted into the vagina in the usual manner with an applicator, or digitally, and it becomes effective directly upon insertion. While it has specific application during the menstrual period, the tampons may also be used at other times during the menstrual cycle when it is desired to overcome a decrease from the normal acidity in the vagina.

It is apparent, that numerous variations, modifications and substitutions may be made in the foregoing illustrative examples while still remaining within the spirit and scope of the invention.

What is claimed is:

1. As a new article of manufacture, an absorbent tampon comprising synthetically modified fibrous material, said fibers being substantially insoluble in water, said fibers having chemically attached cation exchange groups in hydrogen form and being present in suflicient amounts to impart acidifying and bufiering properties to said tampon for maintaining the vagina in an acid condition.

2. As a new article of manufacture, an absorbent tampon comprising synthetically modified cellulosic fibrous material, said fibers being substantially insoluble in water, said fibers having chemically attached cation exchange groups in hydrogen form and being present in suflicient amounts to impart acidifying and buffering properties to said tampon for maintaining the vagina in an acid condition.

3. As a new article of manufacture, an absorbent tampon comprising cellulosic fibrous material, said fibers being substantially insoluble in water, said fibers having chemically attached cation exchange groups in hydrogen form and being present in suflicient amounts to impart acidifying and buffering properties to said tampon for maintaining the vagina in an acid condition in a pH ranging from about 1.5 to about 5.

4. As a new article of manufacture, an abosrbent tampon comprising cellulosic fibrous material, said fibers being of cardable length and being substantially insoluble in Water, said fibers having chemically attached cation exchange groups in hydrogen form and being present in sufficient amounts to impart acidifying and buflering properties to said tampon for maintaining the vagina in an acid condition in a pH ranging from about 1.5 to about 5.

5. As a new article of manufacture, an absorbent tampon comprising a fibrous cellulosic ester, said fibers being substantially insoluble in Water, said fibers having chemically attached cation exchange groups in hydrogen form and being present in sufficient amounts to impart acidifying and buffering properties to said tampon for maintaining the vagina in an acid condition in a pH ranging from about 1.5 to about 5.

6. As a new article of manufacture, an absorbent tampon comprising a fibrous cellulosic ether, said fibers being substantially insoluble in water, said fibers having chemically attached cation exchange groups in hydrogen form and being present in sufficient amounts to impart acidifying and bufiering properties to said tampon for maintaining the vagina in an acid condition in a pH ranging from about 1.5 to about 5.

7. As a new article of manufacture, an absorbent tampon comprising fibrous cellulose phosphate, said fibers being substantially insoluble in water, said fibers having chemically attached cation exchange groups in hydrogen form and being present in sufficient amounts to impart acidifying and buffering properties to said tampon for maintaining the vagina in an acid condition in a pH ranging from about 1.5 to about 5.

8. -As a new article of manufacture, an absorbent tampon comprising cellulosic fibrous material, said fibers being substantially insoluble in Water, said fibers having chemically attached cation exchange groups in hydrogen form and being present in sufiicient amounts to impart acidifying and bufiering properties to said tampon to neutralize from about to about 10 cc.s of menstrual fluid and also to maintain the vagina in an acid condition in a pH ranging from about 1.5 to about 5.

9. As a new article of manufacture, an absorbent tampon comprising fibrous material, said fibers being substantially insoluble in water, said fibers having chemically attached cation exchange groups in hydrogen form and being present in sufficient amounts to neutralize, and to bring to a pH not exceeding about 5, 4 ml. of N/10 sodium hydroxide per gram of fibers.

10. As a new article of manufacture, an absorbent tampon comprising fibrous material, said fibers being substantially insoluble in water, said fibers having chemically attached cation exchange groups in hydrogen form and being present in sufiicient amounts to neutralize, and to bring to a pH not exceeding from about 1.5 to about 5, from about 5 to about ml. of N/ 10 sodium hydroxide.

11. As a new article of manufacture, an absorbent tampon ranging in Weight from about 1.8 grams to about 3 grams and comprising fibrous material, said fibers being substantially insoluble in Water, said fibers having chemically attached cation exchange groups in hydrogen form and being present in suflicient amounts to neutralize,

8 and to bring to a pH not exceeding about 5, from about 3 /2 ml. of N/ 10 sodium hydroxide in the lower part of said tampon sizes to about 12 ml. of N/ 10 sodium hydroxide in the upper part of said tampon weights.

'12. The method of maintaining an acidic condition in the vagina to retard the growth of the pathogenic microorganisms normally associated with nonspecific vaginal infections, said method comprising inserting into the vagina a tampon containing synthetically modified cellulosic fibrous material substantially insoluble in water, said fibrous material having chemically attached cation exchange groups in hydrogen form and being present in sufiicient amounts to maintain the pH of the vagina below 5.

13. The method of absorbing and neutralizing alkaline menstrual fluid during menstruation and maintaining an acidic condition in the vagina to retard the growth of the pathogenic microorganisms normally associated with nonspecific vaginal infections, said method comprising inserting into the vagina during menstruation an absorbent tampon containing synthetically modified cellulosic fibrous material substantially insoluble in water, said fibrous material having chemically attached cation exchange groups in hydrogen form and being present in sufiicient amounts to maintain the pH of the vagina below 5.

References Cited in the file of this patent UNITED STATES PATENTS 2,524,783 Ford et a1. Oct. 10, 1950 2,610,953 Daul et a1 Sept. 16, 1952 2,681,846 Guthrie et al. June 22, 1954 2,856,330 Vagenius Oct. 14, 1958 FOREIGN PATENTS 725,055 Great Britain Mar. 2, 1955 727,631 Great Britain Apr. 6, 1956 748,135 Great Britain Apr. 25, 1956 OTHER REFERENCES Feminine Hygiene Products by M. A. Lesserfrom pages 510-511 and 570-574 of the May 1943 The Drug and Cosmetic Industry (page 571 relied on).

UNITED STATES PATENT OFFICE CERTHHCATE OF'CORRECTFNN Patent No 3 O67 745 December 11 1962 Alfred A. Burgeni et 310 It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as I corrected below.

Column 3 line 74 for "vase read case column 4 in the table column 4 first item thereof for 27.9"

read 279 Signed and sealed this 4th day of June 1963.

(SEAL) Attest:

DAVTDIQIQKDD Commissioner of Patents ERNEST w. SWIDER. Attesting Officer 

1. AS A NEW ARTICLE OF MANUFACTURE, AN ABSORBENT TAMPON COMPRISING SYNTHETICALLY MODIFIED FIBROUS MATERIAL, SAID FIBERS BEING SUBSTANTIALLY INSOLUBLE IN WATER, SAID FIBERS HAVING CHEMICALLY ATTACHED CATION EXCHANGE GROUPS IN HYDROGEN FORM AND BEING PRESENT IN SUFFICIENT AMOUNT TO IMPART ACIDIFYING AND BUFFERING PROPERTIES TO SAID TAMPON FOR MAINTAINING THE VAGINA IN AN ACID CONDITION. 